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This geodatabase was created by the Colorado Geological Survey for the publication ON_008_07_Dakota_Aquifer_Map_of_Colorado.This geodatabase was created in 2022 in ArcGIS for Desktop Version 6.2 (Build 9200) ; Esri ArcGIS 10.8.1.14362The dataset consists of polygon feature classes showing extent of different members of the Dakota Group Aquifer and polyline feature classes of structural elevation contours of contacts between select members and primary structural features. It also includes a point feature class of hydrologic properties of the aquifer. Polygon features and polyline structural feature were compiled from multiple published sources at varying scales from 1:24,000 to 1:250,000 with verification and modification by CGS staff using aerial imagery and DEM raster images. Polyline structural elevation feature classes were generated from multiple sources of point elevation data including surface contacts, permitted water well geologic logs, and geophysical logs of oil and gas wells. The point feature class was generated using calculations using water well production values from permitted water well reports.The Dakota Group in southeastern Colorado consists of three primary members, from to bottom: Dakota Sandstone, Kiowa Shale, and Cheyenne Sandstone. Collectively they are often considered as the Dakota-Cheyenne Aquifer or individually as the Dakota and Cheyenne sandstone aquifers with the Kiowa Shale as a confining layer. The Graneros Shale overlies the group and in most places the Morrison Formation is at the base and both are considered confining layers. Anywhere the Graneros Shale or other Cretaceous and Paleogene formations are present at the surface the entire Dakota Group should be present in the subsurface. Extent polygons are based on contact relations between formations found at the surface and featureclasses in this data set include the contact of Graneros Shale with the Dakota Sandstone as the top of the Dakota Sandstone Aquifer; contact of the Dakota Sandstone with the Kiowa Shale as the base of the Dakota Sandstone Aquifer; contact of the Kiowa Shale with the Cheyenne Sandstone as the top of the Cheyenne Sandstone Aquifer; and the contact of the Cheyenne Sandstone with the Morrison Formation as the base of the Cheyenne Sandstone Aquifer. Structural elevation contour polyline featureclasses are for the top of the Dakota Sandstone Aquifer, top of Kiowa Shale, and base of the Cheyenne Sandstone Aquifer. The contact between the Kiowa Shale and Cheyenne Sandstone can be arbitrary and a polyline structure featureclass has not been included. An outcrop belt polygon featureclass with a featureclass depicting its intersection with the alluvial aquifer area included.Faults displace the Dakota Group which may affect groundwater flow conditions. |